Structural and spectroscopic characterizations of tetra-nuclear niobium(V) complexes of quinolinol derivatives

•Two novel tetranuclear niobium complexes have been synthesized.•Asymmetric oxobridges and nearly linear NbONb bridges have been reported.•The 93Nb NMR spectral results are consistent with the observed data in solid-state.

Reactions between niobium ethoxide and 8-hydroxy-2-methylquinoline or 5-chloro-8-hydroxyquinoline have been explored. Two new tetranuclear heteroleptic niobium complexes containing oxo, ethoxo, and quinolinate chelate rings have been synthesized and characterized by 1H, 13C and 93Nb NMR, UV–Vis, and FT-IR spectroscopies, and single-crystal X-ray diffraction. The molecular structures of the niobium complexes, [Nb4(μ-O)4(μ-OEt)2(ONC10H8)2(OEt)8] (I) and [Nb4(μ-O)4(μ-OEt)2(ONC9H5Cl)2(OEt)8] (II), are composed of a pair of edge-sharing bioctahedral moieties in which connected via two almost linear oxo-bridges, with a large difference in the NbO distances. Single-crystal structures showed both complexes are centrosymmetric and contain two distinct Nb centers, and results confirmed by observation of two niobium signals in the 93Nb NMR spectra of complexes.

Graphical abstractTwo tetranuclear, and centrosymmetric niobium complexes with interesting linear NbONb bond angle were synthesized from 2-methyl and 5-chloro quinolinol derivatives.Figure optionsDownload full-size imageDownload as PowerPoint slide